The proper formation of somatic muscle depends on morphological and molecular events that orchestrate the specification, maturation and terminal differentiation of muscle precursor cells during development. Many of the transcriptional regulatory networks that regulate these processes have been defined, but little is known about the possible post-transcriptional mechanisms that might also be involved. In this issue (), Eric Olson, Aaron Johnson and colleagues conduct a genetic screen for regulators of muscle morphology in Drosophila and identify Hoi Polloi (Hoip), a putative RNA-binding protein with two distinct roles in myogenesis. First, the authors show that Hoip is required for myotube elongation, since elongation failed to initiate in hoip mutants. Second, they show that Hoip is necessary for the expression of sarcomeric proteins Myosin heavy chain (MHC) and Tropomyosin. Importantly, MHC protein expression was restored in the hoip mutant via delivery of a prespliced MHC transcript, suggesting a role for Hoip in pre-mRNA splicing. These data demonstrate a novel and tissue-specific, post-transcriptional role for Hoip in Drosophila development.
